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Journal of Crystal Growth, Vol.367, 126-130, 2013
Directional growth and crystallization of silicon thin films prepared by electron-beam evaporation on oblique and textured surfaces
Electron-beam evaporation (EBE) of silicon permits the high-rate deposition of photovoltaic thin-film devices at low costs. The directional, non-conformal growth characteristic of EBE is systematically investigated by varying the silicon flux angle of incidence gamma on the substrate surface between 0 degrees and 49 degrees. After solid phase crystallization the micro-structural properties of these silicon films are investigated and correlated with the electronic quality of n(+)/p(-)/p(+)-type solar cell stacks. As gamma exceeds 30 degrees, the porosity and oxygen content of the silicon films increase significantly coming along with the break-down of the electronic material quality. At gamma > 40 degrees the silicon crystallization process is even found to be suppressed resulting from a columnar film morphology infiltrated by oxygen-rich pores. The knowledge of this critical angle is essential when textured substrates, consisting of many tilted micro-areas, are used for enhanced light absorption in the silicon film simultaneously ensuring the growth of high-quality material. Furthermore, the inclination angle gamma can serve as design parameter for tailored substrate templates for the fabrication of advanced light-harvesting structures by self-organized solid phase crystallization. (c) 2013 Elsevier B.V. All rights reserved.
Keywords:Solid phase crystallization;Surface structure;Electron-beam evaporation;Oblique evaporation;Silicon thin film;Solar cell